A communication system can be seen as a facility that enables communication sessions between two or more entities such as fixed or mobile communication devices, base stations, servers and/or other communication nodes. A communication system and compatible communicating entities typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. For example, the standards, specifications and related protocols can define the manner how communication devices can access the communication system and how various aspects of communication shall be implemented between communicating devices. A communication can be carried on wired or wireless carriers. In a wireless communication system at least a part of the communication between at least two stations occurs over a wireless link.
Examples of wireless systems include public land mobile networks (PLMN) such as cellular networks, satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN). A wireless system can be divided into cells, and hence these are often referred to as cellular systems. A cell is provided by a base station. Cells can have different shapes and sizes. A cell can also be divided into sectors. Regardless of the shape and size of the cell providing access for a user equipment, and whether the access is provided via a sector of a cell or a cell, such area can be called radio service area or access area. Neighbouring radio service areas typically overlap, and thus a communication in an area can listen to more than one base station.
A user can access the communication system by means of an appropriate communication device. A communication device of a user is often referred to as user equipment (UE) or terminal. A communication device is provided with an appropriate signal receiving and transmitting arrangement for enabling communications with other parties. Typically a communication device is used for enabling receiving and transmission of communications such as speech and data. In wireless systems a communication device provides a transceiver station that can communicate with another communication device such as e.g. a base station of an access network and/or another user equipment. The communication device may access a carrier provided by a station, for example a base station, and transmit and/or receive communications on the carrier.
Examples of communication systems attempting to satisfy the increased demands for capacity are architectures that are being standardized by the 3rd Generation Partnership Project (3GPP), such as the long-term evolution (LTE), or the Universal Mobile Telecommunications System (UMTS) radio-access technologies. The LTE aims to achieve various improvements, for example reduced latency, higher user data rates, improved system capacity and coverage, reduced cost for the operator and so on. A further development of the LTE is often referred to as LTE-Advanced. The various development stages of the 3GPP LTE specifications are referred to as releases.
In LTE-Advanced the network nodes can be wide area network nodes such as a macro eNodeB (eNB) which may, for example, provide coverage for an entire cell. Alternatively in LTE-Advanced, network nodes can be small area network nodes such as Home eNBs (HeNB) (femto cells) or pico eNodeBs (pico-eNB). HeNBs may be configured to support local offload and may support any UE or UEs belonging to a closed subscriber group (CSG) or an open subscriber group (OSG). Pico eNBs can, for example, be configured to extend the range of a cell. In some instances a combination of wide area network nodes and small area network nodes can be deployed using the same frequency carriers (e.g. co-channel deployment). In UMTS multiple base stations (Node-Bs) may be controlled by one or more radio network controllers (RNCs).
Real-time text telephony services may be provided in cellular networks, whereby text can be transmitted as it is being typed or otherwise created (e.g. transcribed from a voice call). Global text telephony (GTT), or teletypewriter (TTY) in public switched telephone network (PSTN), is a real-time text service for deaf and/or hearing impaired persons. In Global System for Mobile communications (GSM) an audio codec, cellular text telephony modem (CTM), is used to transmit the text along a circuit switched (CS) speech call. ITU-T T.140, by the International Telegraph Union Telecommunication Standardisation Sector, defines a protocol for real-time text applications. IETF RFC 4103 defines how T.140 is carried over Real-time Transport Protocol (RTP)/User Datagram Protocol (UDP) in IP networks. IETF RFC 4103 is used for GTT services in Session Initiation Protocol (SIP)/IP Multimedia Subsystems (IMS).
Statement
In a first aspect there is provided a method comprising: sending a message to a node for establishment of a call in an area, said area providing at least partially overlapping packet switched and circuit switched coverage; said message comprising a request for one of a packet switched real-time text component and a circuit switched real-time text component in said call; and in response to receiving a message from said node, sending a further message to said node comprising a request to provide the other of a packet switched real-time text component and a circuit switched real-time text component in said call.
Preferably said message received from said node comprises information that said one of a packet switched real-time text component and a circuit switched real-time text component cannot be supported in said call.
Preferably said method is carried out by a user equipment.
Preferably said message sent to said node comprises a session description protocol message.
Preferably said node comprises a call state control function.
Preferably said packet switched real-time text component comprises a T.140 component and said circuit switched real-time text component comprises a cellular text telephony modem component.
Preferably said call comprises an emergency call.
In a second aspect there is provided a method comprising: receiving a message from a user equipment for establishment of a call in an area, said area providing at least partially overlapping packet switched and circuit switched coverage; said message comprising a request for one of a packet switched real-time text component and a circuit switched real-time text component in said call; and determining whether said one of a packet switched real-time text component and a circuit switched real-time text component can be supported in said call.
Preferably said method comprises sending a message to said user equipment comprising information that said one of a packet switched real-time text component and a circuit switched real-time text component cannot be supported in said call.
Preferably said method comprises receiving a further message from said user equipment comprising a request to provide the other of a packet switched real-time text component and a circuit switched real-time text component in said call.
Preferably said packet switched real-time text component comprises a T.140 component and said circuit switched real-time text component comprises a cellular text telephony modem component.
Preferably said call comprises an emergency call.
In a third aspect there is provided a method comprising: determining loss of a first real-time text component in a call during or after handover of said call from a first connection to a second connection, said first connection comprising one of a packet switched connection and a circuit switched connection, and the second connection comprising the other of a packet switched connection and a circuit switched connection; and in response to said determining, initiating use of a second real-time text component for said call, said second real-time text component being a different type of real-time text component to said first real-time text component.
Preferably said type of real-time text component comprises one of a T.140 component and a cellular text modem component.
Preferably said initiating use of a second real-time text component comprises sending a request to a node.
Preferably said method is carried out in a user equipment.
Preferably said node comprises a call state control function.
In a fourth aspect there is provided a method comprising: receiving a request for support of a second real-time text component of a call during or after handover of said call from a first connection to a second connection, following loss of a first real-time text component in said call, said first connection comprising one of a packet switched connection and a circuit switched connection, and the second connection comprising the other of a packet switched connection and a circuit switched connection; and in response to said request, reserving resources for transcoding of said second real-time text component to said first real-time text component.
Preferably said first real-time text component comprises one of a T.140 component and a cellular text telephony modem component; and said second real-time text component comprises the other of a T.140 component and a cellular text telephony modem component.
Preferably said request is received from a user equipment.
Preferably said method is carried out in a node comprising single radio voice call continuity functionality.
In a fifth aspect there is provided a computer program comprising computer executable instructions which when run on one or more processors perform the method of any of the preceding aspects.
In a sixth aspect there is provided an apparatus comprising at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: send a message to a node for establishment of a call in an area, said area providing at least partially overlapping packet switched and circuit switched coverage, and said message comprising a request for one of a packet switched real-time text component and a circuit switched real-time text component in said call; and in response to receiving a message from said node, send a further message to said node comprising a request to provide the other of a packet switched real-time text component and a circuit switched real-time text component in said call.
Preferably said message received from said node comprises information that said one of a packet switched real-time text component and a circuit switched real-time text component cannot be supported in said call.
Preferably said apparatus comprises a user equipment.
Preferably said message sent to said node comprises a session description protocol message.
Preferably said node comprises a call state control function.
Preferably said packet switched real-time text component comprises a T.140 component and said circuit switched real-time text component comprises a cellular text telephony modem component.
Preferably said call comprises an emergency call.
In a seventh aspect there is provided an apparatus comprising means for sending a message to a node for establishment of a call in an area, said area providing at least partially overlapping packet switched and circuit switched coverage, and said message comprising a request for one of a packet switched real-time text component and a circuit switched real-time text component in said call; and in response to receiving a message from said node, means for sending a further message to said node comprising a request to provide the other of a packet switched real-time text component and a circuit switched real-time text component in said call.
Preferably said message received from said node comprises information that said one of a packet switched real-time text component and a circuit switched real-time text component cannot be supported in said call.
Preferably said apparatus comprises a user equipment.
Preferably said message sent to said node comprises a session description protocol message.
Preferably said node comprises a call state control function.
Preferably said packet switched real-time text component comprises a T.140 component and said circuit switched real-time text component comprises a cellular text telephony modem component.
Preferably said call comprises an emergency call.
In an eighth aspect there is provided an apparatus comprising at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: receive a message from a user equipment for establishment of a call in an area, said area providing at least partially overlapping packet switched and circuit switched coverage; said message comprising a request for one of a packet switched real-time text component and a circuit switched real-time text component in said call; and determine whether said one of a packet switched real-time text component and a circuit switched real-time text component can be supported in said call.
Preferably said apparatus is configured to send a message to said user equipment comprising information that said one of a packet switched real-time text component and a circuit switched real-time text component cannot be supported in said call.
Preferably said apparatus is configured to receive a further message from said user equipment comprising a request to provide the other of a packet switched real-time text component and a circuit switched real-time text component in said call.
Preferably said packet switched real-time text component comprises a T.140 component and said circuit switched real-time text component comprises a cellular text telephony modem component.
Preferably said call comprises an emergency call.
In a ninth aspect there is provided an apparatus comprising means for receiving a message from a user equipment for establishment of a call in an area, said area providing at least partially overlapping packet switched and circuit switched coverage; said message comprising a request for one of a packet switched real-time text component and a circuit switched real-time text component in said call; and means for determining whether said one of a packet switched real-time text component and a circuit switched real-time text component can be supported in said call.
Preferably said apparatus comprises means for sending a message to said user equipment comprising information that said one of a packet switched real-time text component and a circuit switched real-time text component cannot be supported in said call.
Preferably said apparatus comprises means for receiving a further message from said user equipment comprising a request to provide the other of a packet switched real-time text component and a circuit switched real-time text component in said call.
Preferably said packet switched real-time text component comprises a T.140 component and said circuit switched real-time text component comprises a cellular text telephony modem component.
Preferably said call comprises an emergency call.
In a tenth aspect there is provided an apparatus comprising at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: determine loss of a first real-time text component in a call during or after handover of said call from a first connection to a second connection, said first connection comprising one of a packet switched connection and a circuit switched connection, and the second connection comprising the other of a packet switched connection and a circuit switched connection; and in response to said determining, initiate use of a second real-time text component for said call, said second real-time text component being a different type of real-time text component to said first real-time text component.
Preferably said type of real-time text component comprises one of a T.140 component and a cellular text modem component.
Preferably said apparatus is configured to send a request to a node to initiate said use of a second real-time text component.
Preferably said apparatus comprises a user equipment.
Preferably said node comprises a call state control function.
In an eleventh aspect there is provided an apparatus comprising means for determining loss of a first real-time text component in a call during or after handover of said call from a first connection to a second connection, said first connection comprising one of a packet switched connection and a circuit switched connection, and the second connection comprising the other of a packet switched connection and a circuit switched connection; and
in response to said determining, means for initiating use of a second real-time text component for said call, said second real-time text component being a different type of real-time text component to said first real-time text component.
Preferably said type of real-time text component comprises one of a T.140 component and a cellular text modem component.
Preferably said apparatus comprises means for sending a request to a node to initiate said use of a second real-time text component.
Preferably said apparatus comprises a user equipment.
Preferably said node comprises a call state control function.
In a twelfth aspect there is provided an apparatus comprising at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: receive a request for support of a second real-time text component of a call during or after handover of said call from a first connection to a second connection, following loss of a first real-time text component in said call, said first connection comprising one of a packet switched connection and a circuit switched connection, and the second connection comprising the other of a packet switched connection and a circuit switched connection; and
reserve resources for transcoding of said second real-time text component to said first real-time text component, in response to said request.
Preferably said first real-time text component comprises one of a T.140 component and a cellular text telephony modem component; and said second real-time text component comprises the other of a T.140 component and a cellular text telephony modem component.
Preferably said apparatus is configured to receive said request from a user equipment.
Preferably said apparatus is configured to provide single radio voice call continuity functionality.
In a thirteenth aspect there is provided an apparatus comprising means for receiving a request for support of a second real-time text component of a call during or after handover of said call from a first connection to a second connection, following loss of a first real-time text component in said call, said first connection comprising one of a packet switched connection and a circuit switched connection, and the second connection comprising the other of a packet switched connection and a circuit switched connection; and means for reserving resources for transcoding of said second real-time text component to said first real-time text component, in response to said request.
Preferably said first real-time text component comprises one of a T.140 component and a cellular text telephony modem component; and said second real-time text component comprises the other of a T.140 component and a cellular text telephony modem component.
Preferably said apparatus comprises means for receiving said request from a user equipment.
Preferably said apparatus comprises means for providing single radio voice call continuity functionality.